Abstract

The extracellular matrix (ECM) is a complex collection of structural and functional molecules.
Therefore ECM can be defined as “a network of secreted extracellular macromolecules”, and,
depending on the tissue, this network varies greatly in its form and components . A crucial step in
several tissue-engineering techniques is the use of materials which conceivably recreate a spatially
organized bone ECM. Acting as temporary matrix cell guidance they stimulate tissue ingrowth
directly. Because of pivotal role of the ECM in morphogenesis tissue, the basic strategy of the
recent tissue-engineering attempts is mimicking the topological and microstructural characteristic of
bone ECM in a controlled fashion, and providing a mechanical support to the development of new
tissue . An appropriate material for bone repair must possess transversal properties such as
promoting all the specific and biunivocal cell-ECM cross-talks, leading to cell proliferation and the
maintenance of their differentiated functions . Moreover its architectural features are centred on
interconnected macro and microporosity, that ensure mass transfer of nutrients and metabolites and
cellular distribution and migration. Further, the ECM analogs must possess mechanical strength to
withstand the imposed load and let the cells “feel” the right stimuli to produce the right ECM type.
This work is aimed to design and engineeer injectable analogs via innovative realization processes
both for hard tissues, like bone, and for soft tissues like nucleus polposus NP of intervertebral disc.
Two kind of injectable bone analogs were realized: a bioactive foamed injectable paste for bone
repair, that intimate fits complex cavities by using a calcium phosphate and a foamed gelatin gel,
and a bioactive injectable composite paste made up of polycaprolacton and hydroxyapatite obtained
via sol-gel technique. The challenge for any acellular NP replacement material is to mimic the
function of native NP but to date does not exist a defined NP analog because the final results depend
on the synergistic interaction of several parameters of different nature. This experiment campaign
highlight the sophisticated potentiality of natural polysaccarides and collagen gels based on
hyaluronic acid to act as NP replacement.